Geometry questions.

[TexMurphy]

Hi there guys Ive got yet more questions.

First Ive got question about tip and tail. Skis are twintips with a profile of 135-100-125 r20m length 186 running length 155.

What would be your recommendation on tip and tail length (surface) and hight (ground to top)? The design Im currently working with Ive got a tip of about 18cm length and about 5 cm height. I guess if the tip is too long then there will be too much vibration, if its too high (too steep angle) then it will generate too much drag and if its too low then the ski will have tendency to dive.

Im also assuming that one can have a lower tip on a pist ski while one wants a higher tip on a pow ski, correct?

Next thing is about the core.

I assume that one wants the core flat for the binding area but how soon can one start going down?

Ive looked at Kam´s skis in the gallery but since he is using Telemark bindings I assum that he can make his flat area shorter since there is no heel piece and fornt piece is much shorter.

Is there a rule of thumb here? Something like Boot lenght + 20 cm? Or some like that.

Thanks in advance.
Tex

Edit: Added ski dimentions.

[TexMurphy]

Ok got another question about geometry.

Ive got a 8 cm offset on my sidecut radious. Question is should the chamber be offset as well?

What is preferable to have chamber highest point under foot or infront of foot?

Tex

[mark]

For your tip and tail length and hieght, I'd suggest checking out ski manufacturers web sites and looking at specs of comercial skis intended for the same use as what you're building. It may not be perfect but should at least get you in the range that you'll end up with something usable.

8cm offset!

I'm still building my first board, so I may be completely ignorant here, but 8cm offset seems a little much......to me.

[Cadman]

Assuming that your camber is a perfect arc, the highest point of the arc is
generally at the mid point of the running surface length unless you have different distances from the forward effective edge and the rear effective edge. In other words midway from where the bend up points starts at each end.

[iggyskier]

I have 5 different shapes designed right now.

Depending on the ski length and use, the center of the sidecut arc varies a lot based. This spot is also where I plan to mount the skis.

I have 3 pairs which are more directional skis, two 191cm and one 186cm. The mount of the 191cm is -8 and the mount on the 186cm is -6 or -7 I think.

The two more jibby skis I have designed are both 186cm and the mount is about -3 to 3.5

-8cm on a 191cm ski isn't that far back at all, IMO. Very similar to how most people I know mount their ANTs (most I know go -9).